Abstract:

The invention relates to an absorbent adhesive body of a foamed pressure
sensitive hydrocolloid adhesive comprising one or more water soluble or
water swellable hydrocolloids and having gas bubbles incorporated
therein, where the gas in the gas bubbles are in direct contact with said
pressure sensitive hydrocolloid adhesive and where tan δ for said
adhesive in un-foamed form is below 0.35 at 40° C. and 0.001
rad/sec.

Claims:

1. An absorbent adhesive body of a foamed pressure sensitive hydrocolloid
adhesive comprising one or more water soluble or water swellable
hydrocolloids and having gas bubbles incorporated therein, where the gas
in the gas bubbles are in direct contact with said pressure sensitive
hydrocolloid adhesive characterized in that tan δ for said adhesive
in un-foamed form is below 0.35 at 40.degree. C. and 0.001 rad/sec.

2. The absorbent adhesive body according to claim 1 wherein the average
bubble diameter is between 20-80 μm.

3. The absorbent adhesive body according to claim 2 wherein the average
bubble diameter is 30-70 μm.

4. The absorbent adhesive body according to claim 2 wherein at least 95%
of the bubbles have a bubble diameter between 10 and 150 μm.

6. The absorbent adhesive body according to claim 1 wherein the density of
the foamed pressure sensitive hydrocolloid adhesive is below 90% of the
density of the same un-foamed adhesive.

7. The absorbent adhesive body according to claim 1 wherein more than 90%
of the bubbles are closed celled.

8. The absorbent adhesive body according to claim 1 wherein the amount of
hydrocolloid in the foamed pressure sensitive adhesive is above 20% w/w.

9. The absorbent adhesive body according to claim 8 wherein the foamed
pressure sensitive hydrocolloid adhesive comprises a styrene block
copolymer, a tackifier and one or more water soluble or water swellable
hydrocolloids.

10. The absorbent adhesive body according to claim 9 wherein the foamed
pressure sensitive adhesive comprises one or more polyisobutylenes and/or
mineral oil.

11. The absorbent adhesive body according to claim 1 having flat, or
curved first surface adapted to be attached to the skin.

12. The absorbent adhesive body according to claim 11 wherein the adhesive
body is a layer of uniform thickness optionally with a bevelled
peripheral portion, or the adhesive body is a layer, which is thickest in
the central portion and gradually becomes thinner towards peripheral
edge.

13. The absorbent adhesive body according to claim 12 wherein the average
bubble diameter is below 25% of the thickness of the adhesive body where
it is thinnest.

14. A dressing comprising an absorbent adhesive body according to claim 1,
having the surface adapted for being attached to the skin releasable
attached to a release liner and another surface inseparably attached to a
backing layer.

15. A dressing comprising the absorbent adhesive body according to claim 1
as a cushioning element.

16. An ostomy appliance having a wafer or base plate comprising an
absorbent adhesive body according to claim 1.

17. An incontinence device comprising an absorbent adhesive body according
to claim 1.

18. The use of an adhesive body according to claim 1 for attaching an
incontinence device to the skin.

19. The use of an adhesive body according to claim 1 for sealing around a
medical device attached to the skin.

[0002]Hydrocolloid adhesives for skin applications are well known in the
art.

[0003]Hydrocolloid adhesives for skin applications have attractive
features in terms of moisture absorption and price. However, hydrocolloid
adhesives tend to be rough on the skin, and when such adhesives are
removed from the skin, the skin may be stripped of its upper layer.
Changing the adhesive repeatedly as would be the case for e.g. ostomy
appliances leaves the skin damaged and severe pain may be associated with
the removal of the adhesives. The problem can to some extent be handled
by using softer adhesives that deforms more during peeling. When the
deformation is larger, the area over which the peel force is transmitted
to the skin becomes broader leaving the skin less stressed compared to a
harder adhesive with the same peel force. On the other hand, increasing
the softness of the adhesive by modifying the chemical composition
thereof may reduce the structural integrity of the adhesive and the
adhesive may fail cohesively.

[0004]It has now been found that a larger deformation of the same adhesive
when peeling with the same peel force may be achieved by eliminating or
reducing the incompressibility restriction imposed by the solid adhesive
by introducing small bubbles of gas that are able to expand when internal
pressure reduces because of peel deformation of the adhesive mass.

[0005]In this way, the adhesive mass is still incompressible in a
differential fluid element but in a local scale of the size of the
included bubbles, the adhesive mass is compressible and able to expand
with the given flow.

[0006]Introduction of bubbles into an adhesive lowers the modulus of the
adhesive and makes it softer and more flexible. An adhesive comprising
bubbles will have a lower bending resistance than its incompressible
counterpart. This will improve wear comfort.

[0007]A foamed adhesive is also more impact resistant and has a cushioning
effect, because a soft foamed adhesive is able to distribute loads better
and improve pressure relief.

[0008]A disadvantage of the observed in a foamed adhesive is that surface
tension tends to merge bubbles together, leading to larger bubbles. The
density may also increase if bubbles merge with the surface of the
adhesive.

[0009]Porous or foamed hydrocolloid adhesives for medical applications
have already been described in the art.

[0010]Thus, U.S. Pat. No. 4,775,374 describes a skin barrier for use by
ostomates. The barrier makes use of a porous layer of hydrocolloid
adhesive with holes or pores having a size 10-300 μm. The foamed
adhesive layer is thin compared to the bubble size 1-10 mils
(corresponding to 25.4-254 μm) and this construction creates open
pores for gas transport through the adhesive layer. The gas transport in
these adhesives should be within 1-100 cm3/sec/in2 according to
ASTM D-726-71.

[0011]The foamed adhesive body of the present invention differs from the
adhesives described in U.S. Pat. No. 4,775,374 in that the foam is closed
celled and without interpenetrating cavity structure. Furthermore, the
average cell diameter of the gas bubbles in the adhesive body of the
invention is limited to a narrow range of diameters providing the
necessary compressibility.

[0012]U.S. Pat. No. 6,326,524 describe foamed hydrocolloid adhesives with
a bubble size of 200-4000 μm. It is said that the foamed structure of
the adhesive improves absorbency, enables transmission of moisture
through the adhesive, increases flexibility and lowers product cost. The
bubble size is limited to be in the regime 200-4000 μm. The adhesive
used in the example has been tested and was found to be very hard.

[0013]The foamed adhesive body of the present invention differ from the
adhesives described in U.S. Pat. No. 6,326,524 in that the average
diameter of the gas bubbles in the adhesive is much smaller and the
adhesive body is considerably softer which provides the desired broad
peel front. Large bubble diameters may compromise cohesion of the
adhesive body during peeling.

[0014]WO 2004/080498 also suggests absorbent polymer compositions in the
form of foams of a pressures sensitive hydrocolloid adhesive. There is no
information as regards the average diameter of the gas bubbles in these
materials.

[0015]The foamed adhesive body of the present invention differs from the
adhesives described in WO 2004/080498 in that the bubbles in WO
2004/080498 is created using expandable microspheres. These bubbles are
hard as they are incapsulated in a hard material even after expansion.
Thus, such an adhesive would not provide the necessary compressibility
described in this patent.

SUMMARY OF THE INVENTION

[0016]The present invention relates to an absorbent adhesive body of a
foamed pressure sensitive hydrocolloid adhesive comprising one or more
water soluble or water swellable hydrocolloids and having gas bubbles
incorporated therein, where the gas in the gas bubbles are in direct
contact with said pressure sensitive hydrocolloid adhesive and where the
tan δ for said adhesive in un-foamed adhesive is below 0.35 at
40° C. and 0.001 rad/sec.

[0017]In particular the present invention relates to an absorbent adhesive
body as above having gas bubbles incorporated in the pressure sensitive
hydrocolloid adhesive having an average bubble diameter between 20-80
μm.

[0018]The invention also relates to the use of the above-mentioned
adhesive body for various medical applications, such as for attachment of
medical devices to the skin, as a dressing or bandage e.g. for wounds,
and for attachment of ostomy appliances to the skin.

DETAILED DESCRIPTION OF THE INVENTION

[0019]This invention relates to a foamed adhesive body suitable for
various medical applications, in particular within the field of
incontinence, wound care and ostomy care.

[0020]In order to achieve long-term stability of the bubbles it is
necessary to control the elastic and plastic properties of the adhesive.
For a foamed adhesive to remain stable, the adhesive needs to be elastic
at long timescales. On the other hand, if the adhesive is too elastic, it
will no longer be sufficiently adhesive since it is the ability of an
adhesive to `flow` to a surface that makes it a good adhesive. Therefore,
when formulating a foamed hydrocolloid adhesive, it is necessary to have
as high a degree of plasticity at long timescales as possible without the
degree of plasticity being so high that the foamed adhesive is no longer
stable.

[0021]The parameter tan δ as defined in "Dynamics of polymeric
liquids", Vol 1, sec ed 1987, Bird, Armstrong and Hassager, John Wiley
and Sons inc., may be used as a measure of the elastic and plastic
properties of an adhesive. A tan δ=0 corresponds to an ideal
elastic material and tan δ→∞ corresponds to an ideal
liquid. In the definition of tan δ, δ is a function of
frequency where small frequencies correspond to long time scales. Thus,
tan δ at low frequencies provides a measure for the elastic/plastic
relationship at large timescales. For the adhesive to be stable, tan
δ should be small. However, to act as an adhesive tan δ
should be relatively high.

[0022]It has been found, that hydrocolloid adhesives having a tan δ
for the hydrocolloid adhesive in un-foamed form, which is below 0.35,
preferably below 0.30 at 40° C. and 0.001 rad/sec provides a
foamed adhesive with good stability and sufficient adhesive properties.

[0023]Tan δ at 40° C. and 0.001 rad/sec may be measured as
follows: A plate of the un-foamed adhesive material was pressed into a
plate of 1 mm thickness. A round sample of 25 mm in diameter was cut out
and placed in a RheoStress RS600 rheometer from Thermo Electron. The
geometry applied was parallel plates 25 mm and the deformation was fixed
at 1% to ensure that measurements were in the linear regime. The
measurement was carried out at 40° C.

[0024]In one preferred embodiment, the present invention relates to an
adhesive body of a foamed closed celled pressure sensitive hydrocolloid
adhesive wherein the average bubble diameter is between 20-80 μm. In a
preferred embodiment of the invention the average bubble diameter is
30-70 μm.

[0025]According to another preferred embodiment of the invention, at least
95% of the bubbles have a bubble diameter between 10 and 150 μm.

[0026]"Average bubble diameter" means the number average bubble diameter
determined using a microscope mounted with a digital camera. According to
the invention, the average bubble diameter is measured by recording
pictures of the foamed adhesive body and measuring the bubble diameter by
comparing with microscopy pictures of an objective micrometer.

[0027]This method also allows for the determination of the percentage of
bubbles with a diameter within a given range, e.g. a diameter between 10
and 150 μm.

[0028]Varying the foaming conditions may be used to control the diameter
of the bubbles and a person skilled in the art may determine the suitable
foaming conditions. The foaming procedures are described in more detail
below.

[0029]The pressure sensitive hydrocolloid adhesive used for the formation
of the foamed adhesive body should in itself be relatively soft.

[0030]Thus, the pressure sensitive hydrocolloid adhesive composition used
for the preparation of the foamed adhesive body of the invention is
preferably a soft pressure sensitive hydrocolloid adhesive, suitably an
adhesive having a complex modulus below 80 KPa at 1 rad/s at 32°
C., or even more preferred below 60 KPa at 1 rad/s at 32° C. The
complex modulus is defined in "Dynamics of polymeric liquids", Vol 1, sec
ed 1987, Bird, Armstrong and Hassager, John Wiley and Sons inc.

[0031]On the other hand, the pressure sensitive hydrocolloid containing
adhesive mass used for the preparation of the foamed adhesive body of the
invention should not be too soft as this may compromise the cohesion of
the adhesive layer causing the adhesive body to leave residues on the
skin.

[0032]The above-mentioned value for the complex modulus, is the value
obtained by measuring the complex modulus on the unfoamed pressure
sensitive hydrocolloid adhesive using the method described below.

[0033]A plate of the un-foamed material was pressed into a plate of 1 mm
thickness. A round sample of 25 mm in diameter was cut out and placed in
a RheoStress RS600 rheometer from Thermo Electron. The geometry applied
was parallel circular plates 25 mm and deformation was fixed at 1% to
ensure that measurements were in the linear regime. The measurement was
carried out at 32° C.

[0034]The pressure sensitive hydrocolloid adhesive may be based on any
known adhesive mass useful for skin application. A number of pressure
sensitive adhesives may be useful as starting material for the foamed
adhesive bodies according to the invention, see for example the adhesive
compositions disclosed in U.S. Pat. No. 4,551,490, EP 1 021 494 B1, GB 2
300 195, U.S. Pat. No. 4,231,369, U.S. Pat. No. 5,006,401, EP 1 007 597
B1, EP 1 086 189, WO 98/17212, U.S. Pat. No. 5,587,237, WO 02/06687 and
U.S. Pat. No. 4,775,374.

[0035]The pressure sensitive hydrocolloid adhesive used for the
preparation of the foamed adhesive body of the invention, is an adhesive
having a suitable softness, see the values given for the modulus above
and tan δ as described above.

[0036]The hydrocolloid adhesive used for the preparation of the foamed
adhesive body of the invention could be any type of hydrocolloid adhesive
useful for skin applications. In Handbook of Pressure Sensitive Adhesive
Techonology 2nd ed., Satas, editor, (Von Nostrand Reinhold, New York
1989) a number of useful pressure sensitive adhesives are discussed:
A-B-A block copolymer adhesives, amorphous poly alfa olefins, natural
rubbers, polyisoprene, butyl rubber, polyisobutylene, silicones,
polychlorophrene, acrylic adhesives and acrylic dispersions and
polyvinylethers. Any of these pressure sensitive adhesives, or blends
thereof, may be used to produce hydrocolloid adhesives which may be used
to prepared the foamed adhesive bodies of the invention.

[0037]According to a preferred embodiment, the adhesive composition used
for the preparation of the foamed adhesive body of the invention
comprises a cross-linked polyalkyleneoxide polymer, preferably a
polypropyleneoxide polymer.

[0038]According to another preferred embodiment, the adhesive composition
used for the preparation of the foamed adhesive body of the invention
comprises one or more polyisobutylenes, a tri block copolymer, a low
molecular weight diblock copolymer, a tackifier, mineral oil and one or
more water soluble or water swellable hydrocolloids.

[0039]The polyisobutylenes is typically present in an amount from 0% to
50% w/w and suitably has molecular weight between 40 000 and 800 000.
Polyisobutylene is added in order to increase tack and adhesion the skin.
Such polyisobutylenes are commercially available under the trademark
Oppanol from BASF.

[0040]The block-copolymer is typically a styrene block copolymer (e.g. a
SIS, SBS or SEBS tri block copolymer containing a certain amount of
diblock copolymer) and it is present in an amount from 5 to 40% w/w.
Suitable products are commercially available Kraton polmers under the
trademark Kraton, or from Nippon Zeon Co., Ltd. under the trademark
Quintack.

[0041]In WO 99/54422 it is described how the use of diblock copolymers,
such as SI and SB block copolymers in the adhesive composition may
increase the softness and plasticity of the adhesive.

[0042]The low molecular weight diblock copolymer is suitably present in an
amount from 0 to 30% w/w. Suitable di-block polymers are commercially
available from Kuraray under the trademark LIR.

[0043]The tackifier is suitably present in an amount from 0 to 50% w/w.
Suitable tackifiers may be Arkon P70, Arkon P90, Arkon P115 from Arkawa
chemical industries or Regalite R91 or Foral 85 from Eastman.

[0044]The mineral oil is suitably present in an amount from 0-40% w/w. A
suitable mineral oil is Parafluid PL50 from Parafluid
Mineraloelgesellschaft mbH.

[0045]In general the softness of these known pressure sensitive
hydrocolloid adhesives may be improved by regulating the amount of e.g.
mineral oil and plastiziser.

[0047]The hydrocolloids may also be selected from microcolloids (e.g
having a particle size less than 20 microns or preferably below 5 or 2
microns), such as those described in WO 02/06687.

[0048]A suitable hydrocolloid adhesive composition for the preparation of
the foamed adhesive body of the invention comprises:

0%-50% w/w of polyisobutylenes,5%-40% w/w of a triblock copolymer
comprising a certain amount of diblock copolymer,0%-30% w/w of a low
molecular weight diblock copolymer,0%-50% w/w of a tackifier,0%-40% w/w
mineral oil andabove 20% w/w one or more water soluble or water swellable
hydrocolloids.

[0049]The adhesive compositions may optionally comprise further components
normally used in of adhesive compositions e.g. pigments such as zinc
oxide or titanium dioxide, antioxidants etc. The compositions may
optionally comprise minor amounts of conventional plasticizers if special
properties are desired.

[0050]For some purposes it is suitable also to include smaller amounts of
a filler in the mass of the invention which may add to the cohesion and
also contribute to the plasticity. Such filler may e.g. be any filler
known per se for ostomy or wound care purposes such as talc, calcium
carbonate, china clay, zinc oxide or the like. Such filler may constitute
up to 20% by weight of the composition.

[0051]Still further, the adhesive may optionally comprise further
constituents such as emollients, disinfecting agents and/or bactericidal
agents known per se for use for ostomy or wound care purposes.

[0052]Several methods for introducing gas bubbles into an adhesive have
been described.

[0053]Chemical blowing agents or other materials added to the adhesive
formula itself may generate gas bubbles by a variety of mechanisms. These
mechanisms include but are not limited to chemical reaction, physical
changes, thermal decomposition or chemical degradation, leaching of a
dispersed phase, volatilization of low boiling materials or by a
combination of these methods.

[0054]Any of the commercially known chemical blowing agents may be used.
The chemical blowing agents is suitably non-toxic, skin friendly, and
environmentally safe, both before and after decomposition.

[0055]The term chemical blowing agent is used herein to cover the use of
single or multiple component chemicals in a mixture or paste. Suitable
chemical blowing agents include the carbonates, such as ammonium
carbonate, ammonium bicarbonate, sodium carbonate, sodium bicarbonate,
and calcium carbonate. Improved gas generation may be achieved by using a
mixture of carbonates as above and various organic acids including, but
not limited to, stearic, oleic, phthalic, maleic, citric, tartaric acid,
and abietic acids. An excess of organic acids are preferably added to the
carbonates of alkali metals, so the final reaction products have an
acidic character.

[0056]The amount of chemical blowing agent to be added to hydrocolloid
adhesive may suitably range from about 1% up to about 20% by weight. The
amount of gas to be added may be determined by measuring the amount of
gas generated from a candidate mixture and calculating the amount of
foaming required for the final product, tempered by experience of the
amount of gas lost to atmosphere during the foaming process. The creation
of gas bubbles in an adhesive mass by a chemical blowing agent is
described in more detail in U.S. Pat. No. 6,326,524.

[0057]Another method for creating a foamed hydrocolloid adhesive is a
method where a mechanical process is used to add a physical blowing
agent, similar to whipping the adhesive mass into froth, thus creating a
foamed structure. Many processes are possible including processes
involving incorporation of atmospheric air, nitrogen, carbon dioxide, or
other gases or low boiling point volatile liquids during the compounding,
extrusion, converting processes or other manufacturing processes for the
adhesive.

[0058]The pressure sensitive hydrocolloid adhesive may for example be
foamed by mixing the adhesive mass with a gas (air, nitrogen, carbon
dioxide, or other gases), or low boiling point volatile liquids at a
temperature above the melting point of the adhesive at an elevated
pressure (e.g. around 50 bar). The high pressure causes the gas to be
dissolved in the molten adhesive mass. When the pressure is relieved, the
gas starts to flash out of the adhesive mass, which is supersaturated
with gas, both by expansion in un-dissolved bubbles and by forming new
bubbles. The mixture may then be fed through a die or extruder onto a
release liner.

[0059]The creation of gas bubbles in a pressure sensitive hydrocolloid
adhesive may also be achieved by the method described in U.S. Pat. No.
4,775,374 where the components of the pressure sensitive hydrocolloid
adhesive is dispersed in a hydrocarbon solvent such as heptane, or hexane
or mixtures thereof, followed by deposition of a thick layer, for example
by means of a knife-over-roller, of the slurry on a release liner. The
slurry deposited on the release liner is then dried, for example by
passing through a drying tunnel, to achieve a low level of residual
hydrocarbon solvent in the adhesive. The temperature and the time passed
in the drying zone is controlled so that numerous small gas bubbles are
generated from the solvent evaporation.

[0060]The adhesive mass containing the chemical or physical blowing agent
can be processed into foam under any of the techniques described above.
Processing includes forming the adhesive mass into sheet, either flat or
contoured, by extrusion, by pressing, by injection molding, or by
thermoforming or by any other typical adhesive processing method.

[0061]Cutting of the adhesive sheet for a wound dressing or an ostomy
wafer or any other typical shape may be performed either before or after
the foaming of the adhesive mass, depending on the foaming method used.
Suitably, the adhesive mass is foamed during the extrusion process,
followed by calendaring, lamination, and cutting of the foamed sheet into
a specific product.

[0062]A person skilled in the art will be able to select the appropriate
conditions for the process for creation of a foamed adhesive body having
an average bubble size diameter and a bubble size distribution according
to the invention.

[0063]Preferably, the foaming method and the foaming conditions is
selected so that the density of the foamed pressure sensitive
hydrocolloid adhesive is below <0.9 times the density of the same
un-foamed adhesive.

[0064]According to a particular embodiment of the invention, more than 90%
of the bubbles in the absorbent adhesive body are closed celled, which is
an advantage when the adhesive body is used to encapsulate bodily fluids
such as wound exudates or other fluids form the body.

[0065]In one aspect, the invention relates to a medical dressing
comprising a foamed adhesive body of the invention. Such dressings
include wound dressings, burn dressings, blister dressings, fistula
dressings and dressings or bandages having a cushioning effect.

[0066]A dressing or bandage comprising an adhesive body of the invention
usually comprises a backing film or layer on one surface thereof: The
surface of the dressing or bandage, which is to be attached to the skin
may be provided with one or more release liner(s).

[0067]Thus, in one embodiment of the invention, the dressing or bandage
comprising an adhesive body of the invention is a layered product
comprising the adhesive body between a backing layer and a release
liner(s). The invention also relates to such a dressing or bandage where
the release liner is absent.

[0068]The backing layer may be a water impervious layer or film which may
be of any suitable material known per se for use in the preparation of
wound dressings e.g. a foam, a woven or a non-woven layer, a film, such
as a polyurethane-, polyethylene-, polyester- or polyamide film, or a
film with multiple film layers. Suitably the backing layer is permeable
to water vapor. Using a layer or film having a low modulus will also
allow an easy application.

[0069]A suitable material for use as a water impervious film is a
polyurethane. A preferred low friction film material is disclosed in U.S.
Pat. No. 5,643,187. A suitable thickness of this film is below 20
microns. A thickness of about 12-18 microns is preferred for use with
dressings according to the invention, because it results in a significant
decrease of the modulus, compared to a film that is normally used when
preparing medical dressings.

[0070]The water impervious layer or film is preferably a low-friction
flexible polymer film reducing the risk of unwanted stress in the area of
e.g. a crack or wound impeding the healing of such injury on a very
exposed site such as the tip of a finger or toe.

[0071]The adhesive body and the dressing of the invention preferably has
beveled edges in order to reduce the risk of "rolling-up" of the edges
thereof and thereby reducing the wear-time and thus disturbing and
prolonging the healing of cracks normally healing slowly on tips of
fingers or toes due to physical stress. A beveling may be carried out
discontinuously or continuously in a manner known per se e.g. as
disclosed in EP patent No. 0 264 299 or U.S. Pat. No. 5,133,821.

[0072]The adhesive body, or the dressing of the invention may thus be a
layer with a uniform thickness and optionally a beveled peripheral
portion, or the adhesive body or dressing may be a body which is thickest
in the central portion and gradually becomes thinner towards the
peripheral edge. Bandages with beveled peripheral edges are well known in
the art, see e.g. U.S. Pat. No. 4,867,748.

[0073]A release liner may for instance be siliconized paper. The release
liner need not have the same contour as the dressing, e.g. a number of
dressings may be attached to a larger sheet of release liner. The release
liner is not present during the use of the dressing of the invention.
Suitably, the release liner may be removed before or during application
of the dressing.

[0074]The dressing of the invention may comprise a "non touch" grip known
per se for applying the dressing to the skin without touching the
adhesive layer. Such a non-touch grip is suitably formed by the release
liner(s) and is not present after application of the dressing.

[0075]In another aspect, the invention relates to an ostomy appliance
comprising an adhesive wafer or base plate comprising an adhesive body of
the invention.

[0076]An ostomy appliance of the invention may be in the form of a base
plate or wafer forming part of a two-piece appliance or in the form of a
one-piece appliance comprising a collecting bag for collecting the
material emerging from the stoma. A separate collecting bag may be
attached to the base plate or wafer by any manner known per se, e.g.
through mechanical coupling using a coupling ring or through the use of
adhesive flanges.

[0077]An ostomy appliance of the invention also typically comprises a
water impervious backing layer or film, an adhesive body of the invention
and a release liner as discussed above.

[0078]An ostomy appliance of the invention may be produced in a manner
known per se from materials conventionally used for the preparation of
ostomy appliances.

[0079]The adhesive body of the invention may also be used in connection
with incontinence devices, e.g. for attaching such devices to the skin or
as adhesive strips for securing a urisheath during use.

[0083]The SIS/SI copolymer, Polyisobutylene, LVSI and 1/3 of the oil was
mixed in a Z-blade mixer at 140° C. The blend was mixed for 30
minutes to yield a homogeneous mass. The temperature was lowered to
120° C. over 20 minutes while the mass was still mixed. Tackifier
and the remaining oil was added. Mixing continued for 20 min. The
temperature was now again lowered to about 105° C. and the carboxy
methyl cellulose was added and mixing was continued for approximately 15
min until the mass was homogeneous. About 1 kilo of adhesive was prepared
in this way.

Step 2. Foaming

[0084]The adhesive was heated above its melting point to 120° C.
and pumped to a static mixer using a gear pump. The gear pump raised the
pressure of the adhesive to app. 50 bar while the temperature was kept
constant at 120° C. Before reaching the static mixer, a measured
amount of nitrogen gas was continuously added to the adhesive to create a
mixture of gas and adhesive. Concentration fluctuations were reduced by
allowing the mixture to flow through the static mixer. The pressure was
then relieved over a valve. The mixture was feed through a die onto a
release liner to produce an extruded adhesive film of 600 μm in
thickness. Average bubble size was 50 μm with 95% of the bubbles in
the range of 10-150 μm. The density of the adhesive was measured to be
about 80% of the un-foamed adhesive.

Tests

[0085]Un-foamed incompressible adhesives plates of same thickness as in
example 1 were produced for comparison. Both the compressible and
incompressible adhesives were mounted on a polyurethane backing for
peeling. Further, a hard tape was mounted on top of the PU film for the
peeling experiment. For investigating the peel front a setup was
constructed that made it possible to film the peel front in a microscope
(see FIG. 1). The setup moves the substrate right with a velocity v. At
the same time, the peeled adhesive is drawn to the left with the same
velocity v, leaving the peel front area stationary. Peel angle is kept at
180° to mimic a typical peel situation. Through the microscope,
the peel front is filmed and the broadness (I) of the peel front can be
determined by observing the distance from the backing tape to the peel
front line. The broadness I is normalized with the thickness of the
adhesive to yield a dimensionless peel front broadness
b=(I-I0)/I0.

[0086]The peel front broadness was now plotted as function of the adhesive
tested. As a measure of adhesive hardness, we use |G*| at 1 rad/s
measured in a plate-plate rheometer: A plate of the unfoamed material was
pressed into a plate of 1 mm thickness. From this a round sample of 25 mm
in diameter was cut out and placed in a RheoStress RS600 rheometer from
Thermo Electron. The geometry applied was parallel plates 25 mm and
deformation was fixed at 1% to ensure that measurements were in the
linear regime. The measurement was carried out at 32° C. Peel
broadness b for a range of foamed and un-foamed samples are plotted in
FIG. 2. The values in FIG. 2 are measured at 180° peel angle.

Example 2

Measuring Stability of the Un-Foamed Adhesive

[0087]To test stability of foamed hydrocolloid adhesives, a number of
foamed hydrocolloid adhesives were produced. Microscopy pictures were
recorded after the foaming in such a way that the photographed area could
be found again. The samples were stored at 40° C. for five days
and pictures were recorded at the same place as earlier. Before and after
pictures were now compared in terms of bubble stability. When 50% of the
bubbles in the range from 50-100 μm remained stable in this interval
after storage at 40° C. for 5 days, the foamed adhesive was
considered stable. Experiments were performed with adhesives with
different tan δ at 0.001 rad/s measured at 40° C. Results
are tabulated in table 2.

[0088]The results show a clear connection between tan δ at
40° C. and 0.001 rad/s and stability of the bubbles in the foam.
If we extrapolate Adh2 and Adh3 to 50% stable bubbles, we get a tan
δ criterion of tan δ<0.35 at 40° C. and 0.001 rad/s
for bubbles to be stable in a HC foamed HC adhesive.

[0091]The ingredients were mixed in the specified ratios to yield a total
of 20 g. This liquid mass was placed between two pieces of release liner
and pressed at 110° C. At this temperature, the water flashed out
of the hydrocolloid and formed small bubbles in the liquid. At the same
time, the liquid cured and captured the small bubbles in the cured
adhesive and thereby foaming the adhesive. Tan δ=0.05 was measured
for the adhesive at 0.001 rad/s and 40° C. Visual inspection after
storage at 40° C. for 1 month revealed no loss of foam structure
of the adhesive.